The object of the invention is a sampling apparatus in a continuous industrial process for taking a sample of the substance to be monitored, such as a pulp or fluid, the sampling apparatus being placed adjacent to the substance to be monitored, such as on the wall of the pulp tank or liquid tube, and the sampling apparatus including a sample chamber equipped with a cover and a filter for taking the sample from the substance to be monitored through the filter to the sample chamber.
In continuous industrial processes, for example, in the paper industry in processing paper pulp, it is necessary in order to control the process to take samples at different stages of the process. Different sampling apparatuses and sampling methods have been developed for this purpose. The simplest way of taking a sample in a continuous process is to install a tap, for example, in the pulp tank or a tube connected to it. When a sample is needed the tap is turned on. After the sample has been taken the tap is turned off.
However, the known sampling apparatuses have disadvantages. For example, a sample cannot be taken of a thick pulp using a tap, because the pulp clogs the tap. Neither do filters located in conjunction with the tap eliminate these problems, because then the filters easily get clogged.
The purpose of the invention is to eliminate the above-mentioned problem and provide a new sampling apparatus which does not have the above-mentioned disadvantages. It is characteristic of the sampling apparatus relating to the invention that the sample chamber of the sampling apparatus incorporates a closing device, by means of which the connection to the sample chamber from the tank or the like containing the substance to be monitored can be closed, leaving the filter in the sample chamber in a space between the cover and the closing device. Because the filter of the sampling apparatus is cross-directionally smaller than the opening of the sample chamber cover, the filter can be pulled out of the sample chamber after opening the cover of the sample chamber.
According to one advantageous embodiment of the invention, the body of the sampling apparatus""s sample chamber is mainly cylindrical, and the cylindrical filter can be fitted concentrically inside the cylindrical body.
According to another advantageous embodiment, the closing device of the sampling apparatus is an interior cover, which is situated at the end of the cylindrical body that is in the tank or the like containing the substance to be monitored, and the interior cover can be moved in the direction of the axis of the body""s cylinder and pushed against the end of the body to close the sample chamber. In such a case, the interior cover is closed by pulling it against the end of the body by means of actuator cylinders, which are situated between the body and the interior cover.
The actuators can be, for example, pneumatic or hydraulic cylinders. The most advantageous number of actuator cylinders placed at regular intervals on the circumference of the body cylinder is three. The linear motion of the interior cover has been further ensured using three guide bars, which have been placed on the circumference between the actuator cylinders.
According to a third advantageous embodiment, the cylindrical filter is fastened to the interior cover with a screw or the like in such a way that the filter can be unfastened and removed for cleaning.
According to a fourth advantageous embodiment of the invention the closing device of the sampling apparatus incorporates a fixed interior cover or a similar part, which is situated near the end of the cylindrical body that is in the tank or the like containing the substance to be monitored. The closing device has a cylindrical slide, which is moved, for example, by means of a pressure medium and which moves in the direction of the cylindrical body""s axis and presses against the fixed interior cover when closing the device.
Another object of the invention is a sampling method in a continuous industrial process which does not have the disadvantages of the known methods. According to the method, to take a sample of the substance to be monitored, such as a pulp or fluid, the sampling apparatus is placed adjacent to the substance to be monitored, such as on the wall of the pulp tank or liquid tube, and a fluid sample of the substance to be monitored is taken through a filter into the sample chamber.
It is characteristic of the method relating to the invention that the sample chamber of the sampling apparatus is at least partly located inside the tank or the like containing the substance to be monitored, in which case the pressure in the tank presses a fluid sample of the substance to be monitored through the filter into the sample chamber of the sampling apparatus.
According to one advantageous embodiment of the sampling method, the sampling method is continuous in such a way that fluid samples of the substance to be monitored are continuously obtained without disturbing the process taking place in the tank.
In the method, the substance to be monitored, such as, for example, paper pulp, is taken into the sampling apparatus located in conjunction with the tank or the like containing the substance to be monitored, and the pressure in the tank presses the pulp to be monitored against the filter of the sampling apparatus. No suction is used in the method, but instead, normal pressure conditions in the process are utilised. A pressure difference is not produced separately, as there already exists a pressure difference in the process due to the overpressure prevailing in the tank. The filter prevents the passage of solid particles of a predetermined size, but the liquid phase and the colloidal sample phase of the pulp to be monitored are passed through the filter into the sample chamber. From there the sample to be analysed is passed on further for examination.
A further objective of the invention is a method for cleaning the sampling apparatus in a continuous industrial process in which samples are continuously taken from the substance to be monitored, such as a pulp or fluid, and in which a sampling apparatus equipped with a cover is placed adjacent to the substance to be monitored, such as on the wall of the pulp tank or liquid tube in such a way that the fluid sample is taken from the substance to be monitored through the filter into the sample chamber of the sampling apparatus.
The filter of the sampling apparatus is usually the most problematic part of the apparatus because the pulp in the tank tends to clog the filter. In the known apparatuses, it is usually not possible to remove the filter while the process is under way, so there are different methods for cleaning the filter. A generally known method is to arrange a system for blowing air through the filter from the sample chamber towards the pulp tank. In such a case the pulp fibres caught in the filter are released from the surface of the filter and they return to the pulp.
At some stage, however, the filter usually gets so badly clogged, that no air blowing or rinsing procedures can open the pores of the filter. In such a case, the filter needs to be cleaned more thoroughly. This is usually not possible before the process is discontinued and the pulp tank emptied.
The purpose of this invention is to create a method through which the filter of the sampling apparatus can be cleaned without stopping the process. It is characteristic of the cleaning method relating to the invention that the cleaning of the sampling apparatus""s filter comprises the following steps,
the closing device, which is situated at that end where the tank or the like containing the substance to be monitored is, is closed, in which case the process in the tank is not disturbed, but the filter remains in the sample chamber in the space between the cover and the closing device,
the sample chamber is emptied, the cover opened and the filter pulled out for cleaning,
the filter is pushed back to its place, the cover closed and the closing device opened, after which the sampling apparatus is again available for continuous use.
According to one advantageous embodiment of the invention the cleaning of the filter comprises the following steps,
the closing device of the sampling apparatus is closed by pushing the interior cover that can be moved in the direction of the axis of the cylindrical body against the end of the body,
the sample chamber is emptied, the cover opened and the filter detached from the interior cover,
the filter is pulled out for cleaning.
According to another advantageous embodiment of the invention the cleaning of the filter comprises the following steps,
the closing device of the sampling apparatus is closed by pushing the cylindrical slide situated inside the body and moving in the direction of its axis against the fixed interior cover,
the cover of the sample chamber is opened, in which case the filter supported between the cover and the fixed interior cover is released and can be removed for cleaning.